The failure to cure HIV infection is believed to be the result of (1) low level viral production/replication, (2) the presence of latent, replication-competent provirus in quiescent cells, and/or (3) immune dysfunction stemming from chronic activation. None of the currently available antiviral therapies will address the long-lived reservoir of latently infected cells or immune dysregulation. Insights into the cellular mechanisms that control HIV gene expression and chronic immune activation suggest that inflammation-mediated upregulation of negative regulators of T cell activation contribute to the establishment of long-lived latently-infected cells. In this Project, we will explore the role of negative regulators including PD-1 in maintaining latency. In Aim 1 we will determine if, in addition to PD-1, other negative regulators contribute to HIV persistence in blood and tissues from HIV infected individuals receiving suppressive ART. We will assess whether blocking these negative pathways can reactivate viral production in vitro. To optimize this strategy, we will in Aim 2 determine if other therapies can act in concert with PD-1 blockade to disrupt viral latency and/or limit the replenishment of the viral reservoir in vitro. Our studies will focus on the use of agents that are either licensed for use in humans or have progressed sufficiently through preclinical testing at Merck to support chronic dosing in the rhesus model and evaluation in future human trials. Specifically, we will target the IL-10, IFN- a and Notch pathways as these factors impact the proliferation and differentiation of T cells and have an impact upon viral replication. Finally, in Aim 3, we will evaluate the capacity of a PD-1 blocking antibody (in combination with other reagents identified in Aim 2) to impact on latent reservoirs in SIV-infected rhesus macaques receiving suppressive ART. Well characterized, clinical grade anti-PD-1 mAbs are available to test this hypothesis in the rhesus model and will be used to inform rapid progression to clinical studies as appropriate. These studies will address whether blocking PD-1/PDL-1 interactions can result in functional cure, point to adjunct approaches for future studies, and provide potential biomarkers for human clinical trials.